Scanners for facsimile reproduction optically scan an original image to develop electronic signals representative of the image. These signals can be processed, stored, combined with computer generated data, transmitted to other locations and/or utilized in reproduction apparatus to redevelop the image.
Electronic signal representations of images have been transmitted using facsimile equipment in the newspaper industry since as early as the 1940's. Newspapers, such as the Wall Street Journal, pioneered the use of facsimile techniques. Facsimile equipment requires scanners for reading the image and recorders for recording the image. Facsimile technology is used, for example, to prepare negatives from which printing plates are made to print reproductions of optically scanned sheets such as a paste-up of a newspaper page.
When facsimile equipment was first developed for transmitting a scanned image to remote sites, the transmitting site required an operator to load each original page onto the scanner, while the receiving site required an operator to load each sheet of film onto a drum recorder. Transmission at the time was over narrow bandwidth Phone lines. Problems with the facsimile equipment included slow operation and transmission times and inaccuracy of the images upon the film. Because of the labor intensive nature of the equipment and the long transmission times of several minutes for each page, facsimile methods could be tolerated only by newspapers having a national distribution.
For facsimile equipment to be feasible for large metropolitan newspapers, increased speed and improved productivity was required. To improve throughput, wide bandwidth communications were adopted, reducing per-page transmission time to approximately one minute. Line of sight microwave transmissions and then satellite transmissions have reduced the per-page transmission time to approximately 45 seconds. The additional time for loading and unloading between each page of transmission, however, still caused the total time per page to be several minutes. An initial solution was to use redundant equipment in a ping-pong fashion, such that one set of equipment would be loaded while the second set was transmitting or receiving.
One solution in the prior art to decrease loading and unloading time was to replace the facsimile drum recorders with flatbed recorders having on-line film processors and automated feed mechanisms. Dow Jones developed such a device in approximately 1975. The on-line film processor of that system operated with a laser source which recreated the image on a film by modulating a scanner laser beam on and off to expose portions of the film, one scan line at a time. Automated feed mechanisms enabled the receiving equipment to be less labor intensive than in prior systems.
The use of a laser beam for recording and reading enables precise imaging of film. Vibrations of the system, however, can be transmitted to the laser and produce a displaced image at the position scanned by the laser during vibration. The Dow Jones news scanning device referred to above includes a flat optical table mounted to a base with an air suspension system for isolating the optical table from external vibrations. A movable platen resides on the optical table for holding unexposed film that will be imaged or for holding an original that will be scanned. A laser beam scans the film or original along one orthogonal direction, e.g., transversely, while the platen travels continuously at a constant velocity along a second orthogonal direction, e.g., longitudinally. Scanning is effected by deflecting the beam in the scanning direction. As the platen moves, the laser beam scans consecutive lines of, for example, a newspaper page onto the film from left to right across the page in raster fashion.
Because the platen moves under the laser during scanning or imaging, the Dow Jones device must be at least twice the length of the platen. As a result, the device must be of sufficient mass and stability to minimize vibration and maintain accuracy over the entire path of the platen.
Accuracy is an important factor for systems used in the newspaper industry. Newspapers typically require a higher degree of resolution with larger formatted pages and faster throughput than facsimile transmission machines of, for example, inter-office use. Machines capable of achieving higher resolution typically are either too slow or too labor consuming for most newspapers. Additionally, many newspapers now use color formats on some pages. Such color formats require scanners which provide greater resolution and positional accuracy than those intended primarily for black and white reproduction.
One approach for achieving accuracy is to increase the size and mass of the components, thereby achieving better immunity from vibration and better stability. However, the moving parts in these high mass scanners inherently have been burdened with high mechanical accelerations and forces. The momentum attributable to large rapidly moving components in prior art scanners, however, can develop undesirable internal vibrations with a resultant decrease in accuracy.
One object of this invention is to provide an optical scanning system enabling easy loading and unloading techniques to reduce the total per page time to one minute or less. To accomplish this a platen or platens are rotatable between a position for scanning and a position for loading.
Another object of this invention is to provide a scanning system in which the scanner moves over an image area to trace mutually displaced scan lines. This reduces the burdens of the high mechanical accelerations and forces of the massive moving components in the prior art.
It is another object of this invention to provide a scanning system employing a housing having good damping characteristics to substantially isolate the scanner and image area from external vibrations.
In the past images on transparent material have been scanned by placing reflective paper behind the transparency and sensing the reflected beam. A problem with such method is that the reflected beam interferes with the scanning beam causing some inaccuracy. As the precision needs increase this noise in the signals representing the images becomes more significant.
It is therefore an additional object of this invention to provide an optical scanning system capable of scanning images on either transparent or reflective materials.
It is another object of this invention to provide an optical scanning and imaging system having the requisite geometric accuracy resolution, format, and speed for present day electronic imaging and at a cost which is affordable for commercial printing, newspaper, engineering and business applications.
Additional objects of the invention are to provide a scanning device which employs a scanner of reduced size with no loss in scanning accuracy and a scanning beam detector which moves with the scanner.
The present invention encompasses facsimile scanning systems capable of operating either as a scanner for developing electrical signals representing the image which has been scanned, or as a recorder which can reproduce images using a coherent beam that is modulated by the electrical signals to expose a photographic sheet of film.